Fiber lasers have achieved immense output powers with superior beam quality. As the power from a single fiber laser with good beam quality is scaled further to 10 s of kW, it has become more difficult to circumvent nonlinear optical effects and core damage.
A couple methods have been demonstrated to scale the power beyond a single fiber laser power limit. In these approaches, multiple fiber lasers are combined in order to achieve 100s of kW of optical power with good beam quality. One approach is to spectrally combine multiple fiber lasers. In another approach, the fiber lasers are coherently combined.
In the case for coherent combining, a single low power seed is split into multiple beams and seeds all of the amplifiers. The amplifiers amplify the same signal and the output from each amplifier is combined coherently at the output using a number of know methods. As a number of amplifiers increases, so does the overall package weight.
In the case of spectral combining, multiple low power seed lasers, each with different wavelength, are input to their respective amplifiers. The outputs from the amplifiers are spectrally combined using a number of known methods. Needless to say, the overall weight of these systems is also excessive.
The real world solution will require many fiber lasers that are packaged in a compact ultra light weight package. High power fiber lasers have innumerous industrial and military applications. Speaking of the latter, various military carriers, such as tanks, airplanes and the like, are frequently equipped with high power fiber lasers. As well known, the space in these carriers is greatly limited. Typically, fiber laser systems each include a number of stages each consisting of the preamplifier and high power amplifiers. The stages are separated by isolators. The total weight of the combined fiber laser systems is often prohibitively high. As a result, known high power fiber laser systems have an output power to total weight of optical components ratio reaching 0.5 kW per kg.
A need therefore exists for lightweight high power fiber laser systems, utilizing coherent and spectral beam combining, that have power to weight ratios higher than that of the known prior art.